FY 2015 Lake Quinault Nutrient Enrichment

The project elements funded by the grant included 1) fertilizing Lake Quinault with liquid nitrogen and phosphorus fertilizers; 2) monitoring of a suite of physical, biological, and chemical variables relevant to lake nutrient enrichment effectiveness monitoring (Ashley & Stockner 2003); 3)data entry, data QA/QC, and database management; and 4) equipment maintenance/repair and operating expenses. The nutrient prescription is intended to enhance production of edible phytoplankton and zooplankton, the food source of sockeye fry, while avoiding the occurrence of nuisance algae responses. The prescribed nutrient load was developed and then applied weekly by boat from April to October to the epilimnion of Lake Quinault through application of liquid fertilizers urea-ammonium nitrate (32-0-0) and ammonium polyphosphate (10-34-0). The monitor is designed to measure sentinel variables that enable scientists to identify changes in the production cycles of the lake (Stockner 1981, 1987, Shortreed and Stockner 1985). This information chronicled changes in abundance and biomass of major plankton components. Shifts in abundance of species and/or assemblages will signal changes in production, carbon flow, and the food web. The monitor will also provide data to identify physical influences that impact lake productivity (e.g. turbidity influence on euphotic zone depth).

The project benefits (objectives) are 1) supplement natural nutrient loads to Lake Quinault and 2)improve trophic level productivity and lake carrying capacity for sockeye fry. Increased primary productivity is the most consistent measure of nutrient supplementation response in lakes. The prescribed nutrient load is equivalent to a yield of 0.6 ug/L chlorophyll a biomass. QIN will analyze and evaluate the data collected to identify seasonal productivity and report the trophic state of Lake Quinault.